: The primary objective of this proposal is the identification and characterization of the gene responsible for inherited deafness in the mouse mutant known as 'spinner'. Mutation of this gene results in sensorineural hearing loss similar to that found in many human nonsyndromic deafness disorders. The approaches described will attempt to correlate effects at the single gene level with those occurring at the cellular level and the level of the intact cochlea. A positional cloning strategy will be used to identify the affected gene. Gene localization information will be derived from an existing high resolution genetic cross and a set of genomic DNA clones that span the candidate region. Positional candidate genes mapped to this region in mouse, and to the region of conserved linkage in humans, will be evaluated for mutation in spinner mice. To further narrow the candidate region, genomic DNA clones from the candidate region will be microinjected into sr/sr zygotes. DNA clones that contain a functional version of the normal gene are expected to produce phenotypic correction in the resulting transgenic progeny. This DNA will be directly screened for the presence of the affected gene. The biological role of the spinner gene in the cochlea will be examined using several approaches. High resolution phenotypic analysis of affected mice will be performed to identify early defects in the cochlea that result from mutation of the spinner gene. Sensory cell function in the cochlea will be assessed by measurement of evoked responses in spinner mice. Ultrastructural and immunocytochemical analyses will be performed to detail the degenerative process in the mutant cochlea. Database analysis of the gene's primary sequence will be used to identify related genes and protein motifs that may provide insight into gene function. The expression pattern of the spinner gene, and the subcellular localization of its encoded protein, will be determined. Based upon comparative genetic data, the human version of the spinner gene is a positional candidate for the gene affected in a nonsyndromic deafness disorder, DFNB6. The human gene will be directly evaluated for mutations in individuals with inherited defects at the DFNB6 locus. This project will result in the identification of a critical gene in the mammalian inner ear, provide the basis for a model of this gene's role in the cochlea, and investigate the involvement of the gene in human nonsyndromic hearing loss.